The present invention relates to a brake slip-controlled dual circuit vehicle brake system. More particularly, this invention relates to such a system wherein: The brake pedal force is transmitted to a master cylinder and from the latter onto the wheel brake cylinders via a plurality of independently blockable pressure fluid conduits; two pressure modulators are associated with one of the brake circuits respectively; and sensors are associated with the wheels for the detection of a wheel lock tendency as well as for the generation of control signals. With this system the brake pressure at the wheels can be influenced either individually or in groups using the pressure modulators.
A vehicle brake system of this type is disclosed in my co-pending U.S. Application Ser. No. 944,242 filed Dec. 18, 1986. This application corresponds to my German application DE No. 35 45 236 published on June 25, 1987. In the system there disclosed, the pressure modulators are separate assemblies, each of them having its own pneumatic servo drive. They are relatively expensive assemblies and do not ensure that a uniform controlled pressure prevails in both brake circuits when the brake slip control is operative. An equal distribution of the brake force is, of course, highly desirable.